Sometime last year, in December, Mark Gurman from Bloomberg commented on the development of an undisclosed internal project over at Apple called Marzipan. It was rumored to allow apps to be designed simultaneously for both interfaces - iOS and Mac. Then in January this year, Gurman followed up this intel by stating we might see this new functionality arrive with iOS 12 and macOS 10.14, both of which are set to come out this year.
But now, according to another longtime Apple watcher John Gruber, this new initiative is unlikely to surface in 2018, and worst of all, it won’t be as ambitious as we presumed it to be. According to Gruber and his sources, the project has dropped the Marzipan codename and currently seems more “like a declarative control API.” This means it might not equate to a cross-platform development tool but instead allow apps to be built for multiple UI at once. That is to say, the apps would still have to be coded for each platform separately and won’t be helpful in porting iOS apps to Mac.
Here is a more detailed look at what Gruber provided about the rumored internal project:
“It makes sense that if Apple believes that (a) iOS and MacOS should have declarative control APIs, and (b) they should address the problem of abstracting the API differences between UIKit (iOS) and AppKit (MacOS), they would tackle them at the same time. Or perhaps the logic is simply that if they’re going to create a cross-platform UI framework, the basis for that framework should be a declarative user interface.”
Furthermore, Gruber has also stated that there is nearly no chance Marzipan - regardless of what it will be called and what it will end up becoming - will appear at WWDC which is scheduled for June 4th.